The Copper-Chlorine (Cu—Cl) cycle is a thermochemical cycle used for the production of hydrogen, and can be linked with nuclear plants, or other heat sources such as solar and industrial waste heat, to potentially achieve higher efficiencies, lower environmental impact, and lower costs than other conventional hydrogen production technologies.
The Cu—Cl cycle is of interest to Atomic Energy of Canada Limited (AECL) because all of the chemical and electrochemical reactions can be carried out at temperatures that do not exceed about 530° C. This means that the heat requirement of this process can be supplied by the Generation IV Supercritical-Water-Cooled Reactor (SCWR) that is being developed by AECL, which can produce heat at temperatures up to 625° C. The Sodium cooled Fast Reactor (SFR) is another nuclear reactor capable of providing heat at around 530° C. Both the SCWR and SFR, therefore, are ideally suited for electricity production and co-generation of hydrogen.
The Cu—Cl cycle has been developed with several variations, including a four-step process with the following reaction steps:
StepReaction12CuCl(aq) + 2HCl(aq) → H2(g) + 2CuCl2(aq)2CuCl2(aq) → CuCl2(s) (drying step)32CuCl2(s) + H2O(g) → Cu2OCl2(s) + 2HCl(g)4Cu2OCl2(s) → 2CuCl(l) + ½O2(g)
In the four-step Cu—Cl cycle, a chemical species that is consumed in one reaction, such as HCl in Step 1, is produced in a different reaction step, which is Step 3 for HCl. Thus, all of the chemicals are recycled except for water, hydrogen and oxygen, which is consistent with the net reaction being the splitting of water as follows:H2O(g)→H2(g)+1/2O2(g)
In the electrochemical reaction step of the Cu—Cl cycle, the anolyte is a solution of CuCl dissolved in HCl. The catholyte is typically an HCl solution, but in certain variations can be water and in others the catholyte is not required. During the electrolysis step, cuprous ions (Cu+) are oxidized to cupric ions (Cu2+) at the anode while protons are reduced at the cathode to produce hydrogen.
U.S. 2010/0051469 (Stolberg) describes a single membrane electrolysis cell for CuCl/HCl electrolysis. Stolberg demonstrated that a cell configuration of the type shown in FIG. 1 can be used to produce hydrogen by electrolysing a solution of CuCl/HCl at various concentrations of these species.